Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
  • G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
  • G01D5/12—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means
  • G01D5/243—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the phase or frequency of ac

Definitions

• the present invention relates, in general, to sensors which develop signals corresponding to varia ⁇ tions in a parameter being monitored.
• the invention is conce ned particularly with inductance coil sensors and the circuitry for processing the sensor signals to develop indications of changes in the parameter being monitored.
• Non-contacting sensors are well-known. Such sensors may include one or more stationary inductance coils and a movable member which moves in the field of the stationary inductance coils in accordance with the parameter being monitored to change the inductance of the stationary coils.
• Non-contacting sensors are especially useful because they are not subject to wear ⁇ ing as are those sensors in which the moving and sta ⁇ tionary parts are in contact. For example, in a simple potentiometer having a wiper blade which moves along a resistance winding, the constant moving, frictional contact between the wiper blade and the resistance winding will cause wear of one or both parts.
• One technique for processing the signals of an inductance coil sensor to develop an indication of the parameter being monitored involves measuring the effect' of a shif in resonance frequency of a tank circuit which includes, as one of its components, the stationary inductance coil. As the movable member alters the inductance of the stationary inductance coil, a corresponding shift in resonance frequency of the tank circuit is developed.
• Such an approach which may be characterized as time-dependent because frequency is a time-related variable, is to be contrasted with analog techniques, exemplified, for example, by a contacting potentiometer sensor and a non-contacting linear variable differen ⁇ tial transformer (LVDT) sensor.
• analog signal process ⁇ ing techniques are more sensitive to circuit component variations than are time-dependent signal processing techniques.
• analog signal processing tech ⁇ niques require calibration and employ relatively large numbers of discrete circuit components. Consequently, time-dependent signal processing is favored.
• sensor apparatus which includes an inductance coil sensor composed of first and second tank circuits and a movable metal member which when moved, relative to the inductance coil of the firs and the second tank circuits, in accordance with changes in a parameter being monitored changes the relative resonance frequencies of the tank circuits.
• circuit means responsive to changes in the relative resonance frequencies of the tank circuits for developing indications of changes in the parameter being monitored.
• Such circuit means include a pulse generator, a counter and tank circuit switching means. The pulse generator produces a first series of pulses having a repetition rate corresponding to the resonance frequency of the first tank circuit and a second series of pulses having a repetition rate corresponding to the resonance frequency of the second tank circuit.
• the counter responsive to the first and second series of pulses, counts a prescribed number of pulses of the first series and the same number of pulses of the second series and develops a first counter output pulse having a duration proportional to the time required to count the prescribed number of pulses of the first series and a second counter output pulse having a duration proportional to the time required to count the prescribed number of pulses of the second series.
• the tank circuit switching means connect the first and the second tank circuits to the pulse gener ⁇ ator in timed alternating sequence.
• Figure 1 is a perspective view of one induc ⁇ tance coil sensor which may be used in the present invention
• Figure 2 is a circuit diagram of one pre ⁇ ferred embodiment of sensor apparatus constructed in accordance with the present invention.
• Figure 3 is a series of waveform diagrams useful in understanding the operation of the Figure 2 circuit
• FIGS 4A, 4B and 4C are schematic diagrams of three different types of tank circuits which may be used in the Figure 2 circuit;
• Figure 5 is a circuit diagram of a second preferred embodiment of sensor apparatus constructed in accordance with the present invention.
• Figure 6 is a series of waveform diagrams useful in understanding the operation of the Figure 5 circuit
• Figure 7 is a circuit diagram of a third preferred embodiment of sensor apparatus constructed in accordance with the present invention.
• Figure 8 is a series of waveform diagrams useful in understanding the operation of the Figure 7 circuit.
• an inductance coil sensor which may be used in the present invention includes an insulating board 10 having first and second stationary inductance coils 12a and 12b. As shown, stationary inductance coils 12a and 12b may be planar and formed by conventional printed circuit.
• a movable member 14 which serves as a spoiler as it moves above stationary inductance coils 12a and 12b.
• Spoiler 14 in the form of a planar metal part, is mounted on a shaft which, in turn, is coupled to another rotating component (not shown), the movement of which represents the parameter being monitored.
• Figure 2 which is a circuit diagram of one preferred embodiment of sensor apparatus constructed in accordance with the present invention, shows how an indication of the position of spoiler 14 is developed.
• Stationary inductance coils 12a and 12b and a capacitor 16 form a pair of tank circuits which are connected, in timed alternating sequence, to frequency sensing means composed of a pulse generator 18 and a counter 19.
• coils 12a and 12b are switched, in timed alternating sequence, to the input of pulse generator 18 by a switching circuit composed of a pair of tran ⁇ sistors 20 and 22, a pair of resistors 24 and 26, and an inverter 28.
• the tank circuit composed of stationary inductance coil 12a and capaci ⁇ tor 16 or the tank circuit composed of stationary inductance coil 12b and capacitor 16 is connected to pulse generator 18.
• Waveforms (A) and (B) of Figure 4 represent the two different resonance frequencies of the two tank circuits.
• the higher frequency of wave ⁇ form (B) represents the condition of spoiler 14 being more in the vicinity of stationary inductance coil 12a than in the vicinity of stationary inductance coil 12b.
• Waveform (C) represents the output of pulse generator 18. During those periods when coil 12b is connected to pulse generator 18, the repetition rate of the output of the pulse generator corresponds to the resonance frequency of the tank circuit formed by coil 12b and capacitor 16. During those periods when coil 12a is connected to pulse generator 18, the repetition rate of the output of the pulse generator is higher and corresponds to the higher resonance frequency of the tank circuit formed by coil 12a and capacitor 16.
• the output of pulse generator 18 is supplied to counter 19 which measures the amount of time re ⁇ quired to count a specific number of pulses. For the example shown in Figure 3, four pulses, two positive- going and two negative-going, are counted, and after the prescribed number of pulses have been counted, a new count is started. With the start of each new count, the output of counter 19 changes level to form pulses having durations corresponding to the time re ⁇ quired to count the prescribed number of pulses. This is shown in waveform (D) in Figure 3.
• the higher level of the counter output signal represents the resonance frequency of the tank circuit formed by stationary inductance coil 12b and capacitor 16, while the lower level of the counter-output signal represents the resonance frequency of the tank circuit formed by sta ⁇ tionary ' inductance coil 12a and capacitor 16.
• the relative time durations of the counter pulses of wave ⁇ form (D) provide an indication of the position of spoiler 14 relative to coils 12a and 12b.
• the output of counter 19 also controls the operation of the switching circuit which switches the input of pulse generator 18 between coils 12a and 12b.
• An output indication, representative of the position of the spoiler, is developed by an inverter 32, a first RC circuit composed of a resistor 34 and a capacitor 36, and a second RC circuit composed of a resistor 38 and a capacitor 40.
• the signal at a ter ⁇ minal 42 between resistor 34 and capacitor 36 has a value proportional to:
• FIGS 4A, 4B, and 4C show schematically three different types of tank circuits which may be used in the Figure 2 circuit.
• the tank circuits in Figure 4A represent the ones shown in Figure 2.
• a switch 46 represents the action of the Figure 2 switching circuit in connecting either stationary in ⁇ ductance coil 12a or stationary inductance coil 12b to the pulse generator (not shown) to form one or the other of the tank circuits with capacitor 16.
• Spoiler 14 also is shown in Figure 4A and its movement is represented by the double-ended arrow.
• the tank circuits have a single stationary inductance coil 48 which is connected to the pulse generator (not -shown). Coil 48 is switched, in timed alternating sequence, by the switching means, represented by a switch 50, between two capacitors 52 and 54 ' to form the two tank circuits.
• the two tank circuits each have a stationary inductance coil 56 or 58 and a capacitor 60 or 62.
• the two tank circuits are switched, in timed alternating sequence, by the switching means, repre ⁇ sented by a switch 64, to the input of the pulse gener ⁇ ator (not shown).
• the stationary inductance coils shown as planar coils
• the spoiler shown as a planar solid member
• the stationary induc ⁇ tance coils may be wound and the spoiler may be a planar coil.
• the second embodiment of the present inven ⁇ tion is generally similar to the first embodiment, shown in Figure 2. Elements in Figure 5 corresponding to elements in Figure 2 have been given the same reference numerals.
• the pulses from pulse generator 18 are supplied to the counter portion 66 of a counter/timing circuit unit to develop a count ⁇ er output signal such as the one represented by wave ⁇ form (D) of Figure 37
• Waveform (E) of Figure 6 shows two cycles of the counter output signal for two differ ⁇ ent positions of the sensor spoiler.
• the counter output signal is supplied to integrating means which develop an integration signal, represented by waveform (F) in Figure 6, composed of a rising portion developed during time T ⁇ from the positive-going first counter output pulse and a decay ⁇ ing portion developed during time T 2 from the negative- going second counter output pulse.
• the integrating means include a resistor 67 and a capacitor 68.
• the integrating means also include a second resistor 69 to which an inverted version of the counter output signal is sup ⁇ plied. This arrangement having a pair of integration circuits with a common capacitor, provides a differen ⁇ tial output across capacitor 68 proportional to:
• Such switching means may include an electronic switch 70 which selectively couples the counter signal to the integrating circuit composed of resistor 67 and capaci ⁇ tor 68 and an electronic switch 71 which selectively couples the inverted version of the counter signal to the integrating circuit composed of resistor 69 and capacitor 68.
• Switches 70 and 71 are controlled by the timing circuit portion 72 of the counter/timing circuit unit which supplies a first control signal along an output line 73 to switches 70 and 71 to disconnect counter 66 from the integrating circuit composed of resistor 67 and capacitor 68 and to disconnect counter 66 from the integrating circuit composed of resistor 69 and capacitor 68.
• the first control signal supplied by timing circuit 72 is represented by waveform (G) in Figure 6 and is effective in interrupting development of the integration signals.
• Waveform (H) represents the effect of the first control signal from timing circuit 72 on the development of the integration signal developed at the junction of resistor 67 and capacitor 68.
• An identical signal, but oppositely directed to the one represented by waveform (H) is developed at the junction of resistor 69 and capacitor 68.
• switches 70 and 71 are closed and capacitor 68 functions in the usual way in charging and discharging according to the signals supplied by counter 66.
• the level of the first control signal drops to zero, switches 70 and 71 open and the condition of capacitor 68 remains unchanged while the switches remain open.
• the levels of the integration signals remain at the levels at the start of the interruption. This is represented by the flat portions of waveform (H).
• switches 70 and 71 are again closed by the control signal, capacitor 68 re ⁇ sumes charging and discharging according to the signals supplied by counter 66.
• the timing of the closing of switches 70 and 71 is selected at the mid-points of the rise and decay portions of the integration signals to approximate the average levels of the integration signals. As will become apparent, the durations of the closing of switches 70 and 71 can be relatively short and shorter than illustrated in waveforms (G) and (H). However, timing circuit 72 is simplified by making the open time of switches 70 and 71 equal to the closed times which precede and follow the open times, thereby centering the interruptions of the development of the integration signal in the rising and decaying portions of the integration signal.
• a capacitor 73 serves to store the levels of the integration signals during periods of interruption in the development of the integration signals.
• Dis- posed between capacitor 73 and the integrating circuits are second switching means for selectively connecting the integrating circuits to this capacitor.
• Such switching means may include a pair of electronic switches 74 and 75 which selectively transfer the level of the integration signals to capacitor 73 during selected interruptions of the development of the inte ⁇ gration signals.
• Switches 74 and 75 also are controlled by timing circuit 72 which supplies a second control sig ⁇ nal along an output line 76 to switches 74 and 75 to connect capacitor 73 to capacitor 68.
• the second con ⁇ trol signal supplied by timing circuit 72 along output line 76 is represented by waveform (I) in Figure 6. This signal is composed of pulses which are present during selected open times of switches 70 and 71 during the decay portions of the integration signal and sample the level of the integration signal during these peri ⁇ ods of interruption of the development of the integra ⁇ tion signal. In this way, the control signal supplied to switches 74 and 75 is effective in transferring the level of the integration signal, as shown by the second flat portion of each cycle of waveform (H), to capaci ⁇ tor 73.
• Waveform (J) in Figure 6 represents the level of the integration signals transferred to capacitor 73.
• the integrating means in ⁇ clude only one integration circuit or two integration circuits arranged to develop a differential signal. The only difference between the two is the magnitude of the signals. If greater accuracy is required, both the levels of interruption during the rise portions and the levels of interruption during the decay portions can be sampled with the output signal being developed by aver ⁇ aging the two.
• Figure 7 which is a circuit diagram of a third preferred embodiment of the present invention, illustrates that the present invention can be employed in sensing relative movements within a moving assembly.
• One such application of the present invention is sens ⁇ ing the twist imparted to a torqued rotating shaft.
• the dashed lines in Figure 7 represent the placement of those components within the dashed lines on a moving as sembly, such as a steer ing co l umn of an automobil e.
• the remaining components are on a sta ⁇ tionary assembly which is mechanical ly isolated from the moving assembly.
• Serial No. 757 ,726 filed July 22 , 1985 and en ⁇ titled "Sensor Apparatus” illustrates a sensor unit which can be empl oyed in the Figure 7 embodiment of the present invention.
• a pair of inductance coils 80 and 82 ( Figure 7) , can be carried, as shown in application Serial No.
• Inductance co il s 80 and 82 and a capacitor 88 form a pair of tank circuits which are connected, in timed alternating sequence, through a pair of electron ⁇ ic switches 90 and 92 controll ed by a first logic and control circuit 93 to a first pul se generator 94.
• the control of electronic switches 90 and 92 wil l be des- cribed shortly.
• Pulse generator 94 produces pulses at a repe ⁇ tition rate corresponding to the resonance frequency of the particular tank circuit connected to the input of the pulse generator.
• the resonance frequencies of the two tank circuits are determined by the inductances of the coils 80 and 82 which, in turn, are dependent upon the position of vane 84.
• the combined effect of the two tank circuits and pulse generator 94 is generally similar to the combined effect of the corresponding elements in the circuits of Figures 2 and 5, except that in the circuit of Figure 7 the switching between inductance coils 80 and 82 is separated by fixed peri ⁇ ods of time during which power is transmitted to the moving assembly.
• a second logic and control circuit 98 which turns on a second pulse generator 100 to produce a fixed rate series of pulses.
• a counter 102 counts a prescribed number of these pulses and conditions logic and control circuit 98 to supply a timing signal which controls transmission of power to the moving assembly.
• Power is supplied by a first tri-state driver composed of three inverters 104, 106 and 108.
• Inverters 104 and 106 are controlled by the timing signal supplied by logic and control circuit 98.
• the output from pulse generator 100 is supplied directly to inverter 104 and through inverter 108 to inverter 106.
• Waveforms (K) and ( ) of Figure 8 represent the pulses supplied to inverters 104 and 106, respectively.
• Waveform (M) of Figure 8 represents the tim ⁇ ing signal supplied by logic and control circuit 98.
• Timing signal pulse ' causes the tri-state driver to be connected to winding 96b for the duration of pul se Pi .
• Waveform (N) of Figure 8 represents the power ⁇ ** ⁇ transmitted to the moving assembly through transformer 96 and results from the oppositely directed pulses produced by inverters 104 and 106 being supplied to opposite ends of winding 96b.
• This power is supplied to an AM detector 110, connected across winding 96a, and a peak detector 112 which together form a power supply and function in the usual manner to develop a power supply voltage represented by terminal 114.
• This power supply voltage operates electronic switches 90 and 92, logic and control circuit 93, pulse generator 94, and an inverter 116.
• the actual connections be ⁇ tween terminal 114 and the units powered by the supply voltage at this terminal have been omitted from Figure 7 for the sake of clarity.
• the output of AM detector 110 also controls the operation of logic and control circuit 93. This is accomplished by detecting the timing signals which control the transmission of power to the moving assem ⁇ bly. For the duration of the first timing signal pulse p ⁇ , logic and control circuit 93 inactivates electronic switches 90 and 92, so that pulse generator 94 also is inactive and power can be transmitted from winding 96b to 96a.
• timing signal pulse P lf inverters 106 are inactivated, so that the transmission of power- is interrupted and the ends of winding 96b float.
• This condition is detected by AM detector 110 and logic and control circuit 93 is condi ⁇ tioned ' to close electronic switch 90 and thereby con ⁇ nect the tank circuit composed of inductance coil 80 and capacitor 88 to the input of pulse generator 94.
• Pulses having a repetition rate corresponding to the resonance frequency of this tank circuit are transmit ⁇ ted from winding 96a through winding 96b to counter 102.
• counter 102 After counter 102 has counted a prescribed number of pulses, it generates a counter output pulse having a duration proportional to the time required to count the prescribed number of pulses. This is represented by pulse « L of waveform (M) of Figure 8 which corresponds to pulse Ti of waveform (C) of Figure 3.
• logic and control circuit 98 supplies a second timing signal pulse P 2 which activates inverters 104 and 106 to transmit power to the moving assembly.
• pulse P 2 is detected by AM detector 110, so that logic and control circuit 93 inactivates electronic switches 90 and 92 for the duration of pulse P 2 .
• Pulse generator 94 responsive to the second tank circuit, develops a second series of pulses having a repetition rate corresponding to the resonance fre ⁇ quency ' of the second tank circuit. These pulses are transmitted through transformer 96 to counter 102 which counts the prescribed number of pulses and develops a
• second counter output pulse having a duration propor ⁇ tional to the time required to count the prescribed number of pulses of the second series. This is repre ⁇ sented by pulse T 2 of waveform (M) of Figure 8 which corresponds to pulse T of waveform (C) of Figure 3 but is separated in time from pulse T ⁇ because of the intervening transmission of power during pulse P 2 .
• timing signal pulses P ⁇ and P 2 are different so that logic and con ⁇ trol circuit 93 can distinguish between the two and thereby activate the appropriate electonic switch 90 or 92 associated with the tank circuit which is to be connected to pulse generator 94 following the particu ⁇ lar power transmission.
• the counter output pulses - ⁇ and T2 are sup ⁇ plied from logic and control circuit 98 to a second tri-state driver composed of inverters 120 and 122 which are controlled by the logic and control circuit to pass the first counter output pulses T* ⁇ to a first RC circuit composed of a resistor 124 and a capacitor 126 and the second counter output pulses T 2 to a second RC circuit composed of a resistor 128 and a capacitor 130.
• the difference in the signals at a pair of ter- minals 132 and 134 is proportional to:
• T ⁇ + T 2 represents the position of vane 84 relative to inductance coils 80 and 82.

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Measurement Of Length, Angles, Or The Like Using Electric Or Magnetic Means (AREA)
• Measurement Of Unknown Time Intervals (AREA)
• Measurement Of Resistance Or Impedance (AREA)
• Investigating Or Analyzing Materials Using Thermal Means (AREA)
• Investigating Or Analyzing Materials By The Use Of Fluid Adsorption Or Reactions (AREA)

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• 1986
  • 1986-01-29 US US06/821,982 patent/US4663589A/en not_active Expired - Lifetime
  • 1986-02-10 DE DE8686901278T patent/DE3677087D1/de not_active Expired - Lifetime
  • 1986-02-10 AU AU54526/86A patent/AU581972B2/en not_active Ceased
  • 1986-02-10 WO PCT/US1986/000284 patent/WO1986004670A1/fr active IP Right Grant
  • 1986-02-10 EP EP86901278A patent/EP0211901B2/fr not_active Expired - Lifetime
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